3. INDEX
● INTRODUCTION AND BACKGROUND
● DESIGNING CONSIDERATIONS
● DRS SYSTEM DESIGN
❖ AERODYNAMIC STUDY
❖ ACTUATION TYPE
❖ STRUCTURE DESIGN AND SIZING
❖ ELECTRIC AND ELECTRONIC DEVICES
● STEERING WHEEL DESIGN
❖ CONCEPT DEFINITION
❖ PROTOTYPE
❖ FORCE ANALYSIS
❖ FINAL DESIGN
● CONCLUSIONS AND CONSIDERATIONS
● REFERENCES
10. 1) FEMALE END ROD
.3R = 2 * r
R ) .62 0 m A = π * (
2
− r 2
= 8 * 1 −6 2
R ) .67 0 m I z = 4
π
* ( 4
− r 4
= 8 * 1 −12 4
80 MPa σ x max = A
Nx
+ wz
Mz
= 4
.8 mm, R .84 mm r = 0 = 1
σ = π E I2
* *
4 A L * *
2
To avoid buckling we have new restrictions. Solving the formula we obtain that:
.008 mm, R .31 mmr = 1 = 2
However, to fit in the actuator bar, it will have to be oversized. With this calculations we know
that we can choose the smaller end rod that fits in the main rod.
2) ROD 2 (CONNECTION BETWEEN WINGS)
h = 3 * b
A = b * h
I z = 1
12 * b * h 3
11. 92.8 MPa σ x max = A
Nx
+ wz
Mz
= 1
.55 mm, h .65 mm b = 1 = 4
σ = π E I2
* *
4 A L * *
2
To avoid buckling we have new restrictions. Solving the formula we obtain that:
.33 mm, h 0 mmb = 3 = 1
3) RODS 3 AND 4 (CONNECTION BETWEEN ACTUATOR AND WING)
h = 5 * b
A = b * h
I z = 1
12 * b * h 3
92.8 MPa σ x max = A
Nx
+ wz
Mz
= 1
.37 mm, h 1.85 mmb = 2 = 1
σ = π E I2
* *
4 A L * *
2
In this case, solving the buckling formula we obtain lower values than the ones calculated to
avoid plastification. Buckling doesn’t restrict the area in this case.
13. Figure Exploded view
Figure: Detailed view
System components. Technical drawings
1. M6 thin nuts x 10 units: Their function is blocking the rotation of the shafts fixing them
to the anchor plates´ rods. (no drawings, standard parts available)
2. Actuator support bracket: This part will receive compression force from the actuator.
The surface is glued to the lower spoiler´s surface using 3M special adhesives for
carbon fiber parts.
14. 3. Actuator housing: The actuators cover to perfectly fit the cylinder and enabling the
rotation due to the incorporated drilled extension where is build.
4. Threaded shaft x 3 units: (no drawings, standard parts available)
5. Extended rod end
6. Klicktronic actuator: Electric actuator to supply an instant movement.
7. Connecting rods
15. 8. Anchor plate (medium spoiler, named 3): Junction structure between the extended
end rod that enables to transform the linear movement into rotation of the wing.
9. Anchor plate (Higher spoiler, named 4): Junction structure between the rods that
enables to transform the linear movement into rotation of the higher wing.
10. Spacer: To block the axial displacement of the rods that are connecting medium and
high spoilers (no drawings, standard parts available).
27. MECHANICS
The main difficulty of the drs mechanics part was manufacturing a precise and lightweight
structure and parts to accomplish the desired obtain ratios that where previously calculated
and forecasted to end up with the optimum open position. We have gone through a different
difficulties throughout the manufacturing which lead us to make small refinements for the
manufacturing part.
About the structure, we went through a small problem in our manufacturing for the brackets.
At first, we calculated the required parameters considering our material thickness and
properties which result on: Bend Allowance 0.57” and Minimum Bend Radius 0.32”. Having our
bracket process fully defined, we did our CAD drawings and export them to dfg format to cut
them in the waterjet. After having our cutted part ready we started with the bending
process. Assisted with help from the machine shop we realized that the bending machine was
not able to produce our desired bending parameters due to the lack of a tool measure. As a
result, bend Radius too small and bending separation too narrow forcing the fracture of the
part.
Facing this early problem on the manufacturing, we did a quick redesign for welding so we
could cut each brackets in 3 different pieces and weld them using the gap and avoiding the
bending problems.
The cutting and tolerance involved on the assembly were successful which took as to the
welding process. We used standard tungsten EDM electrodes to unify the three parts and after
finishing that with sand the junctions to ensure the surface quality.
28. The next step, was the glued area testing. Our purpose was testing the properties of 3M
adhesive between two materials of different nature. Carbon fiber samples were
manufactured to simulate wings surface as well as the aluminum samples. Using the tensile
testing machine located in the machine shop we get an outstanding performance of more that
10 times the force required for our drs application.
Testing results:
Shear resistance: 2500 lbs,
Requirements: 230 lbs
For the shaft size, drill size is dependent in the standarized tables. Having ¼ inch shafts
already purchased the drill size is defined on the standarized tables. The shaft were threaded
using ¼ inch 20 corse thread type on both sides of the shaft, leaving the middle section
smooth surface to contact the bearing inside ring.
Sideway picture of the wing. Bearings placed on rotation points. Pressure + Glue combination
method was used to ensure the total fixture of them. We built blocking nuts to lock
disassembly.
29. Drilling the spoilers was quite challenging due to the geometry of the latter made impossible
to use a fixture for machining. Knowing that the only chance was going for the craft method.
We used a custom made support to keep the drill straight during the whole stroke.
Parts disassembly
•Double sealed bearings
•Nuts
•Welded brackets
•4 x shafts: ¼ inch 20 thread.Threaded-smooth-
threaded sections
•Connecting rods
•Plastic spacers
30. ELECTRONICS
The goal of implementing an electronic system controlled by Arduino comes for several
reasons. Firstly, the linear actuator has a DC motor inside that provides the power to create
movement. We want to inverse the voltage when we want to change the position of the rear
wing and only electric devices can’t accomplish that in a simple way. Besides, the system is
also controlled by the brake, so we want to manage both inputs correctly with a program. And
last but not least, the Arduino allows keeping improving the system. It could be made
completely automatic with more inputs such as speed and turning sensors.
We have used the software 123d circuits from Arduino to create a digital model and try
different configurations and testing. The schematic view is the following.
As we can see we are using an Arduino micro and a motor driver. Specifically, it is an h-bridge.
The DC motor represents the linear actuator and the pushbuttons represent the inputs from
the steering wheel and brake.
The LED allows the driver to know the current position of the drag reduction system. The
resistor previous to it just limits the current that goes through the LED, protecting it from
overloads.
About the motor driver, in this scheme the model is L293D. However when we tested the
system, the current provided by this device was too low to move the actuator fast enough.
That’s why we changed it for a more potent version called L298.
L293D L298
32. Testing Process
In order to save as much money as possible we started testing with a small DC motor, so we
make sure the most expensive devices are protected until we make sure the system works.
Once we figured out that the program worked exactly as we wanted we went ahead and
connect the linear actuator. A more powerful battery was necessary as well to provide enough
current.
Finally, we put the breadboard into a waterproof project box and we change the wires for
those which specifically fit the dimensions of the car. In order to make the steering wheel
detachable we used professional contacts.
Besides, the pushbutton in the brakes used for testing was changed for a pressure switch. This
makes the braking process more reliable to deactivate the system as soon as the driver
brakes.
33. STEERING WHEEL
The steering wheel work for the manufacturing semester was challenging. Our main objective
was to develop the process for efficiently fabricate the carbon fiber steering wheel
accomplishing all of our design requirements, such as a 60% of weight reduction, increase the
ergonomics and upgradeability. There were several steps to follow in order to end up with a
well fabricated product.
During the winter break we were able to improve the design of the whole steering wheel. We
refined the shape and managed to improve the Carbon Fibers layout in Solidworks to 5 layers
(15, 75,0,75,15 degrees) achieving a safety factor of 2.68.
Mold Design and Manufacturing
The steering wheel requires a two-piece mold to be manufactured in order to achieve the
hollow body we are aiming for. To do so, it is needed to design a CAD model of each mold and
create different CNC machining toolpaths.
The first step is to generate the CAD files of the molds. They are based on cutting the
Steering Wheel’s CAD in half with a specific “tangent cut” throughout the whole surface. This
is done in order to have all the surfaces of each mold going from perpendicular to parallel in
the direction of “pulling out”. Next we can see two pictures representing the mold’s surface.
Red is the portion of the surface that needs to be cut considering the “tangent cut”.
Green: Front side mold; Grey: Back side mold; Red: Portion that needs specific cut
34. Once the CAD files are designed, the next step is to generate the CNC Machining Toolpaths.
For this we used the integrated CAM software for Solidworks called HSM Works. This software
allows you to generate different kinds of “passes" around the 3D file and apply parameters
like speed of the tool spinning & moving, dimensions of the drill, material to be drilled,
height of steps, etc. To give an example, a higher speed of the drill makes it easier and safer
to remove material. But on the other hand, it can lead to overheat the material and start
deforming, so there is always compromise between the speeds, time and material. For this
design and the smooth surface we needed, we decided doing two passes, a rough one with a
½ inch standard tip drill and a second and slower for the finish with a rounded tip ¼ inch.
The material we used for the molds is a High Density Foam called RenShape 5045, with a
density of 30 lbs/ft3. This type of Foam is widely used for machining molds for small scale
objects due to its good mechanical properties and easiness to machine and prepare. The
machining time for each mold was 3-4 hours.
Preparing the Mold’s Surface
Next step is to prepare the surface, covering all the pores of the material itself and little
holes that the machining process left. For this, we used West Systems resin resources:
Epoxy Resin (covering pores), Fast and Slow Hardeners (resin catalysers), Microspheres (Fine
glass bubbles to cover holes and scratches), plastic cups and scrapers. The mixture ratio of
the resin is 5 part resin to 1 part hardener. Microspheres are added to give consistency
without increasing weight for the holes.
35. After applying 3-4 layers of resin and all the pores and holes are covered, sanding is required.
Handsanding with 500 grit paper will remove all the extra resin while leaving a scratchy
surface for a primer to be applied. The polymer based primer is applied in order to build a
thin layer of non stick material. After that, wetsanding by applying water to the mold and
using first 800 grit paper followed by 1200 grit for a smooth finish.
The last step for the surface preparation is to apply a chemical release agent so that the
carbon fibers and resin that will lay on top of it won’t stick to the mold and will be easy to
take out.
Carbon Fiber Layout and Bonding
Once the molds are prepared and ready to use, the carbon fiber layout is followed. Trying to
accomplish our layers direction and place, we managed to lay down the 5 layers of carbon
fiber mixed with resin at a 60% carbon - 40% resin ratio. Next step is to apply a foam material
as a “breather" and put both molds inside a vacuum bag. Vacuum is applied at 30 inHg while
breather soaks the extra resin. The resin needs to cure for as long as 48 hours preferably at a
temperature of 200-250 Fahrenheit degrees for this type of resin.
After the resin is cured, some strength is needed to pull the carbon fiber out of the mold.
Then, excess is trimmed and front and back sides are ready to be bonded together.
Finally bonding both sides together was a mind teaser. The aim was to create a “lip" in
between both sides that mimics the inside surface of each, so that it can be glued and
secured perfectly. To do so, we laid a carbon fiber lip around the inside and built a bag on
36. the inside too. Then we put the second half of the steering wheel on top and applied vacuum
in between the bag and the whole carbon fiber steering wheel so that the bag expands and
pushes the lip against the two.
The steering wheel at this point is completely manufactured. Below is a comparison between
the old and heavy metal frame steering wheel and our new carbon fiber one. We achieved an
improvement of 50% in weight with only 0.6lb. It improves ergonomic by being also
upgradable.
At the end we were able to complete this project on time, with great results. We had to try
different times to completely achieve our goals and we learned a lot about how to design and
manufacture an engineering project. We are proud of our results and hope we can apply our
learning from this whole project in the future.